1. Field of the Invention
The present invention relates to a method of assembling a power brake assembly including a master cylinder and a brake booster.
2. Description of the Prior Art
Vehicles often include a hydraulic or power braking system for reducing the speed of the vehicle and/or maintaining the vehicle in a stopped position. Typically, the power braking systems include a brake booster having an output rod, which is received by a master cylinder. Hydraulic brake lines fluidly couple the master cylinder to one or more hydraulic brake wheel cylinders. The brake booster receives a pedal rod, which is coupled to a brake pedal positioned within a cabin of the vehicle. In operation, the brake booster reduces the force required to activate the braking system by amplifying a force exerted on the brake pedal by an operator of the vehicle. The brake booster transmits the amplified force through the output rod to one or more pistons disposed within the master cylinder. Movement of the pistons within the master cylinder provides fluid under pressure to each brake wheel cylinder through the hydraulic brake lines.
The pistons within the master cylinder typically include bypass apertures that must be closed off or covered by seals in order to develop the pressurized fluid which is provided to each brake wheel cylinder. Because of dimensional variations in the master cylinder and brake booster, the seals and bypass apertures are positioned a distance from one another. This distance, known in the art as travel-to-close, must be traveled by either the piston and/or the output rod before the pressurized fluid in the master cylinder is developed. As such, this distance gives rise to pedal travel which affects the pedal feel for an operator of the vehicle. Accordingly, methods of assembling power brake assemblies have made various attempts to reduce this distance or travel-to-close to improve pedal feel.
One method of assembling a power brake assembly is disclosed in U.S. Pat. No. 4,400,942. The method of assembly includes the insertion of a master cylinder into the brake booster, after which a tubular collar of the brake booster is crimped about a radial shoulder of the master cylinder to secure the master cylinder to the tubular collar. However, any method disclosed in U.S. Pat. No. 4,400,942 is not concerned with controlling pedal travel loss either before or after securing the master cylinder to the brake booster.
Other methods of assembling the power brake assembly attempt to control pedal travel by axially adjusting the output rod of the brake booster during assembly to prevent the piston of the master cylinder from being too far back in a chamber of the master cylinder and thus far away from the output rod. One example is disclosed in US Patent Application Serial No. 2002/0124390 in which the method of assembly includes adding and longitudinally positioning a cap on the output rod for allowing the cap to narrow a gap between the output rod and the piston of the master cylinder. Other methods of adjusting distances between components of the power brake assembly occur after the master cylinder and brake booster have already been secured relative to one another. One such example is disclosed in U.S. Pat. No. 4,545,206 which discloses an apparatus for adjusting a magnitude of clearance between a reaction disc and a reaction transmitting member of the power brake assembly. However, the aforementioned methods of controlling pedal travel loss can be very cumbersome and time-consuming.